目的探讨2005年11月1日发生5例不明原因重症肺炎(治愈3例、死亡2例)的发病原因,提出鼠疫自然疫源地调查,确定疫源地的存在。方法采用常规调查方法,通过血清学,鼠疫菌学,基因诊断学等技术进行判定。结果共分离到8株鼠疫杆菌,疫区犬血清阳性率22.99%,猫阳性率21.21%。结论细菌学证实丽江发现鼠疫自然疫源地,并处于流行活跃阶段,发现鼠间有鼠疫的流行。 Objective To investigate the causes of 5 cases of unexplained severe pneumonia (3 cases were cured and 2 died) on November 1, 2005. The investigation was made on the natural foci of plague and the existence of foci was determined. Methods The methods of routine investigation were used to determine whether they were serological, plague bacteriological and genetic diagnosis. Results Eight strains of Yersinia pestis were isolated. The positive rate of serogroups was 22.99% in dogs and 21.21% in cats. Conclusion bacteriological confirmed Lijiang natural plague plague found, and in the popular stage of the epidemic, found a plague epidemic in rats.